Identifying mediums using optical characteristics are known, and the color of the identifying medium may be varied by tilting, and a latent image may be viewed (or become invisible) in observation through a polarizing plate. The identifying medium may be used as a device for determining whether or not various kinds of articles are authentic, for example. As the identifying medium, for example, identifying mediums disclosed in Japanese Patent Application Laid-Open No. 63-51193 and Japanese Patent Application Laid-Open No. 4-144796 are known.
The identifying medium may be used by affixing it to an article to be identified. In this case, if the identifying medium that is affixed to an article can be easily peeled off, the identifying medium may be reused and be misused. Therefore, the identifying medium is affixed to the article by a special adhesive agent so that it cannot be easily peeled off. In addition, the identifying medium is formed with a feature such as a cut, so that the identifying medium will split if it is peeled off, in order that the identifying medium cannot easily be reused, while maintaining the prior condition.
In a case of an article (object to which an identifying medium is affixed) made of a liquid-penetrable material, when a certain kind of organic solvent penetrates into the article, the bonding strength of an adhesive agent is decreased. Therefore, there may be a case in which the identifying medium can be peeled off without breaking. In this case, the identifying medium can be reused and may be misused.